The invention relates to real time systems diagnostics, and more particularly, to a technique for analyzing the response time of a plurality of disk drives for such machines.
The need to process vast quantities of information has become much more crucial as electronic imaging machines become more complex and versatile. The necessity of processing large blocks of data can be very important to the efficient operation of the machine. This can be particularly important in retrieving and printing data from a plurality of disk storage devices sharing portions of the information to be processed. In a real time system, access times of disks must be predictable to insure that data is read correctly. Storage devices that are not predicted accurately can result in erroneous or garbled data being retrieved, stored, or printed.
The prior art includes U.S. Pat. No. 4,870,643 to Bultman et al. discloses a parallel drive array storage system which includes five disk drives, a formatter for each drive, and a master controller. The spindles of each drive rotate in synchronism to improve data handling. Information is routed successively to the first four drives, while the fifth drive has parity check information. The system is capable of running even if one of the drive units fails. Various low level diagnostics are available for determining faults. Synchronization of the drives is accomplished by a spindle reference counter which provides an index pulse to each individual drive for controlling its rate of rotation. See Col. 18, line 41 through Col. 20, line 58.
U.S. Pat. No. 4,731,673 to Yamakawa discloses an image output device which has a plurality of memories, each capable of reading and writing parallel data, a data reading instruction means, and a plurality of dot forming means. A clock signal is used for parallel transfer of image data between the plurality of memories.
U.S. Pat. No. 4,564,864 to Maeshima discloses an image forming apparatus capable of accurately recording image input information and driving plural recording units simultaneously even when a recording unit is not synchronized with the input information.
A difficulty with the prior art systems is that the systems are often simply redundant systems or only tested memory drives individually rather than in relation to one another or are directed to the recording of information rather than to synchronized retrieval from a plurality of memories for printing.
It is an object, therefore, of the present invention to test the retrieval of data from a plurality of disk memories in relation to one another against a threshold value to uncover a relatively slow drive response. Other advantages of the present invention will become apparent as the following description proceeds, and the features characterizing the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.